The French patent application published under number 2 783 336 describes a card comprising electrical contacts for communicating in accordance with a universal serial bus (USB) standard. The card has external electrical contact areas compatible not only with ISO standard 7816 which defines standard cards, but also with USB standard version 1.1 of Sep. 23, 1998.
A problem encountered is described below with reference to accompanying FIGS. 1 and 2.
FIG. 1 shows part of a card body 10 made of plastics material and having an electronics module 12 received therein represented by its external contact areas 14 for providing electrical connections between the integrated circuit of the electronics module 12 and contact elements of the connector 16 shown in FIG. 2. As a general rule, the various contacts are constituted by a single conductive coating made on the contact face of the module and etched so as to define different external areas. With a standard module, there is a first area 18 that constitutes the ground contact and that generally extends into a central zone 20 of the face of the electronics module, a VCC area 22 for supplying electrical power to the electronics module, a VPP area 24 for applying a write voltage for the memories of the electronics module, an RST area 26 for resetting auxiliary circuits of the electronics module to zero, an area 28 for receiving a clock signal CLK, and an I/O area 30 for inputting and outputting data interchanged between the electronics module of the card and the card reader. Two areas 32 and 34 remain available. For a card that complies simultaneously both with ISO standard 7816 and with the USB standard, the external areas 32 and 34, conventionally referred to as D+ and D−, serve as serial data inputs for providing a higher rate of information interchange between the card and the reader. The areas 18 to 34 are distributed in two rows that extend perpendicularly to the direction in which the card is inserted into the reader.
FIG. 2 shows the connector 16 of the card reader which essentially comprises a frame 36 having two parallel series of resilient contacts 38 and 40 fixed thereon for coming into electrical contact with respective ones of the external areas. The various resilient contacts 38 and 40 are connected to a processor circuit 42 of the reader. In FIG. 2, arrow F shows the direction in which the card C is inserted into the reader, and the term “insertion edge” is used to designate the edge A of the card body 10 adjacent to which the electronics module 12 is located.
It will be understood that given the geometrical disposition of the external areas which are in alignment via their edges and of the resilient contacts 38 and 40 of the reader which are also in alignment, connection between the resilient contacts of the reader and the external contact areas of the card takes place simultaneously for all eight external areas of the electrical contact.
For standard cards complying with ISO standard 7816, this situation does not present any drawback since the connector remains unpowered until the card has been fully inserted. In contrast, with cards that comply with the USB standard, this situation is unacceptable, and in particular it is not acceptable that the electrical power supply voltage for the circuits of the electronics module as applied between external areas 18 and 22 might be applied after information signals are applied to the areas 32 and 34. The standard requires that the element plugged into the USB connector must be capable of being plugged in while the connector is powered. In addition, the standard specifies that power supply and ground must necessarily be connected before all of the other contacts.